The present application relates to construction equipment, such as cranes. In particular, the present application relates to a crane having several unique and inventive aspects, such as a self-raising mast, a hydraulic circuit for raising the mast, and a microprocessor-based controller for controlling the mast raising procedure. The present application also relates to a method of self-raising the mast and assembling the crane.
Construction equipment, such as cranes or excavators, must often be moved from one job site to another. Moving a crane or an excavator can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed, and overhead obstacles can dictate long, inconvenient routings to the job site.
One solution to improving the mobility of large construction machines, such as cranes, is to disassemble them into smaller, more easily handled components. The separate components can then be transported to the new job site where they are reassembled.
The typical practice has been to use an assist crane to disassemble the crane into the separate components. The assist crane is then used to load the components onto their respective transport trailers. Once at the new job site, another assist crane is used to unload the components and reassemble the crane. As the components for a large crane can weigh as much as 80,000 lbs., the capacity of the assist crane required represents a very significant transport expense.
As a result, designers have attempted to develop self-handling systems for assembling and disassembling cranes. The majority of the self-handling systems developed thus far have been directed to smaller cranes that only need to be disassembled into a few components.
The development of self-handling systems for larger cranes, however, has met with limited success. One reason for this is that larger cranes need to be disassembled into numerous components, thus requiring time-consuming disassembly and reassembly procedures. For example, a large capacity crane typically uses a complicated and cumbersome rigging system to control the angle of the boom. Boom rigging system components such as the equalizer, the mast, and wire rope rigging are heavy and difficult to disassemble for transport. Another reason for the limited success of prior art self-assembling cranes is that they typically rely on additional crane components that are used only for assembling and disassembling the crane. For example, some self-assembling cranes require additional wire rope guides and sheaves on the boom butt so that a load hoist line can be used with the boom butt to lift various crane components during the assembly process.
An example of a prior art method for assembling and disassembling a typical large capacity crawler crane is disclosed in U.S. Pat. No. 5,484,069, titled xe2x80x9cProcess For Self-Disassembling A Crawler Cranexe2x80x9d (xe2x80x9cthe ""069 patentxe2x80x9d). In particular, this patent is directed to a type of crawler crane having a mast that is supported by a backhitch.
Another example of a prior art method for assembling and disassembling a different type of crawler crane is disclosed in U.S. Pat. No. 6,062,405, titled xe2x80x9cHydraulic Boom Hoist Cylinder Cranexe2x80x9d (xe2x80x9cthe ""405 patentxe2x80x9d). This patent is directed to a type of crane that utilizes hydraulic cylinders to control the angle of the boom.
The ""069 patent and the ""405 patent are both examples of self-assembling cranes that require the use of the boom butt to lift and position components for assembly on to the crane. As a consequence, additional sheaves must be included on the boom butt for the self-assembling procedure. It is therefore desirable to provide a crane and method of self-assembly which eliminates, or at least reduces, the use of the boom butt during the self-assembling procedure.
In addition to the above, some types of cranes utilize a moving or live mast. A crane having a moving or live mast is connected directly to the boom by one or more boom pendants. The boom angle is controlled by boom hoist rigging, which is connected between the mast and the upper works of the crane. The mast and the boom move together as the boom angle is changed. The mast must typically be disconnected from the boom and stored horizontally on top of the crane for transport between job sites. Moreover, the masts on these types of cranes are often very long and heavy, and are consequently difficult to handle during the assembly process. It is therefore desirable to provide a crane having a self-raising mast. It is also desirable to provide a system and method of controlling the mast self-raising procedure that is safe, efficient and easy to implement.
In preferred aspects, the present invention comprises a crane having an upper works rotatably mounted on a lower works, a boom pivotally mounted on the upper works, a mast pivotally mounted on the upper works and pendantly connected to the boom, and boom hoist rigging connected to the mast for controlling the angle of the boom. The invention further comprises a self-raising mast assembly for controlling the position of the mast when the mast is not connected to the boom. The self-raising mast assembly comprises a mast raising yoke, a hydraulic mast raise cylinder, and a hydraulic system.
The mast raising yoke is pivotally connected to the upper works and preferably has an axis of rotation that is aligned with the axis of rotation of the mast. The mast raising yoke is configured to engage and support the mast when the mast is not within the mast operating range, and is disengaged from the mast when the mast is within the mast operating range, the mast being supportable by the boom hoist rigging when the mast is within the mast operating range.
The hydraulic mast raise cylinder is pivotally connected between the upper works and the mast raising yoke. The hydraulic mast raise cylinder is extendable and retractable so as to rotate the mast raising yoke. The hydraulic system controls the extension and retraction of the hydraulic mast raise cylinder.
The preferred method of self-raising the mast comprises the steps of first engaging the mast with the mast raising yoke when the mast is in a rearwardly extending stored position on a rearward portion of the upper works, then extending the mast raise cylinder to rotate the mast raising yoke in a first direction so as to pivot the mast upwardly from the stored position to a forwardly leaning position. When the mast is in the forwardly leaning position, the mast is then supported with the boom hoist rigging, while the mast raise cylinder is retracted to rotate the mast raising yoke in a second direction so as to disengage said mast raising yoke from the mast. The boom hoist rigging is then extended to lower the mast towards a forwardly extending fully forward position in front of the upper works, where it is then engaged by the mast raising yoke. The mast raise cylinder is then extended to rotate the mast raising yoke in the first direction so as to pivot the mast downwardly to the fully forward position. The mast can then be connected to the boom.
The self-raising mast assembly and method permits the mast to be raised and lowered during the assembly process without the need for a separate crane, and overcomes many of the problems identified above. In particular, the self-raising mast assembly and method permits the mast to be raised from and lowered to a stored position on the rearward portion of the upper works. The assembly and method also permits the mast to be raised from and lowered to a fully forward position in front of the upper works. Moreover, the assembly and method permits the mast to be used for lifting and assembling crane components during the crane self-assembly and self-disassembly process.
These and other advantages, as well as the invention itself, will become apparent in the details of construction and operation as more fully described and claimed below. Moreover, it should be appreciated that several aspects of the invention can be used with other types of cranes, machines or equipment.